The applicant's career goal is to become a cardiovascular surgeon-scientist conducting translational basic science and clinical research in cardiovascular diseases. To this end, he will obtain a masters degree in Clinical Investigation while pursuing basic research to augment his previous experience. Monocytes/macrophages are important in angiogenesis and muscle regeneration. Monocyte chemotactic protein-1 (MCP-1), and its specific CC chemokine receptor, CCR2, are important determinants of monocyte/macrophage recruitment to injured tissues. Our lab has documented that MCP-1 -/- and CCR2 -/- mice exhibit impaired muscle regeneration and increased adipocyte accumulation in injured muscle after ischemic muscle injury in association with impaired monocyte/macrophage recruitment. Preliminary studies with CCR2 -/- mice after toxic muscle injury have demonstrated similar impairments in monocyte/macrophage recruitment and muscle regeneration as well as having impaired angiogenesis and delayed restoration of tissue vascular endothelial growth factor (VEGF) levels. Furthermore, bone marrow- derived cell(s) are responsible for impairments in both angiogenesis and muscle regeneration. Since CCR2 also has profound effects on multiple bone marrow-derived cells including other inflammatory and endothelial progenitor cells, we hypothesize that the recruitment and activation of monocytes/macrophages are essential for angiogenesis and the normal regeneration of muscle after injury. The proposed studies will determine the contribution of monocytes/macrophages to angiogenesis and muscle regeneration using an unique transgenic mouse (CD11b-DTR) which permits the conditional, specific ablation' of monocytes/macrophages with the following specific aims: 1) determine the effects of early vs late monocyte/macrophage ablation on angiogenesis, adipocyte accumulation and muscle regeneration, 2) determine the effects of monocyte/macrophage ablation on tissue and plasma levels of MCP-1 and VEGF, and 3) determine the effects of monocyte/macrophage ablation on MPC accumulation. This proposal will determine the effects of monocyte/macrophage ablation at early and late time points after injury on inflammation, angiogenesis and muscle regeneration after injury. Limb amputations are common in patients after traumatic extremity injury and peripheral arterial disease despite vascular bypass techniques and angioplasty. A better understanding of the complex interactions of inflammatory cells, angiogenesis and muscle regeneration could lead to new therapies for limb salvage for ischemic or traumatic injuries and an improved understanding of skeletal muscle engineering. [unreadable] [unreadable] [unreadable] [unreadable]